Electrode mounting structure for cathode ray tubes

ABSTRACT

A character display system has a plurality of small cylindrical side-by-side cathode-ray tubes about .8 inch in diameter and less than 4 inches long, aligned to form a line of individual characters. The tubes have structure for precisely aligning the characters uniformly including an electron gun fashioned to center the electron beam by means of electrostatic deflection electrode pairs held in two glass beads oriented with a seven pin miniature glass stem to produce two normal deflection axes. Similar electrode structure is employed for a plurality of electrodes in the gun formed of a rectangular shaped blank held at opposite ends in the two beads, and a set of snubber springs is affixed to one such electrode oriented toward the stem to and in centering the gun within the tube cylindrical walls.

United StatesQPatent Inventor Horst H. Blur'nenberg Owensboro, Ky. Appl.No. 861,600 Filed Sept. 29, 1969 Patented Feb. 16, 1971 f AssigneeKentucky Electronics, Inc.

Owensboro, Ky. Continuation-impart of application Ser. No. 843,296, July22, 1969.

ELECTRODE MOUNTING STRUCTURE FOR CATHODE RAY TUBES 3 Claims, 5 DrawingFigs.

US. Cl 313/82; 313/5 3131251 Int. Cl. H0lj 29/02, H0 1 j 29/46 Fieldol'Sear-ch 3 l 3/109.5, 82

References Cited UNITED STATES PATENTS 2,266,773 12/1941 Law 313/82X2,496,825 2/ 1950 Szegho 313/82 2,516,704 7/1950 Kohl 313/7 2,781,4742/1957 Coleman 315/21 2,859,378 11/1958 Gundert et al... 315/132,975,315 3/1961 Szegho 313/82 3,215,880 11/1965 Krackhardt 313/82FOREIGN PATENTS 957,087 5/1964 Great Britain 313/82 PrimaryExaminerRobert Segal Anomey Laurence R. Brown ABSTRACT: A characterdisplay system has a plurality of small cylindrical side-by-sidecathode-ray tubes about .8 inch in diameter and less than 4 inches long,aligned to form a line of individual characters. The tubes havestructure for precisely aligning the characters uniformly including anelectron gun fashioned to center the electron beam by means ofelectrostatic deflection electrode pairs held in two glass beadsoriented with a seven pin miniature glass stem to produce two normaldeflection axes. Similar electrode structure is employed for a pluralityof electrodes in the gun formed of a rectangular shaped blank held atopposite ends in the two beads, and a set of snubber springs is affixedto one such electrode oriented toward the stem to and in centering thegun within the tube cylindrical walls.

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" RACTER GENERAT I 1 AND SELECTION CIRCUITS l5 FIG.|

INVENTOR ATTORNEY HORST H; BLUMENBERG PA ENI n rm 1 s an f, sum 2 ur z'if I YIII/IIIIIII. 'IIIIIIIIIIA INVENTOR HORST H. BLUMENBERG ATTORNEYELECTRODE MOUNTING STRUCTURE FOR CATHODE RAY TUBES This application is acontinuation in part of my copending U.S. application for indiciaForming Cathode Ray Tubes, Ser. I

No. 843,296, filed July 22, 1969.

This invention relates to character display devices and moreparticularly it relates to cathode-ray tube displays for generating aline of separate characters in individual side-by-side tubes.

Display devices responsive to electronic signals to generate visualcharacters such as numbers or alphabets are known, which operate indifferent modes. Many such devices are deficient in several importantaspects.

If mechanical devices are used, they do not follow electrical signalsadequately or quickly enough and they are difficult to synchronize.

Cathode glow and phosphor display devices are low in brightness. Most ofthese provide parallax problems and do not show parts of the charactersformed. Also they are not adaptable to variations of characters and suchsymbols as the dollar sign or letters in Hebrew or Arabic which requirespecialtooling. Also a limited number of different characters can bedisplayed, in general. v

Cathode-ray tube devices in the prior art have not been competitive inprice with low-cost display tubes. Some have required custom tubes withbuilt in masks or special features for generating character shapes.Generally, an entire line of would require custom built envelope sizesand specialized deflection systems. Individual tubes used for generatingeach character would be too expensive in both tube design and systemrequirements when using prior art techniques. For example oscillographiccentering structure such as horizontal and vertical centeringpotentiometers used in orienting placement and skew of the differentcharacters placed ina line by means of standard CRT techniques would beprohibitive in price when applied to a plurality of individual tubes.

Accordingly, it is an object of this invention to provide improvedcharacter display devices correcting the foregoing deficiencies.

A more specific object of the invention is to provide speciallyconstructed cathode ray tube indicia generating devices which areeconomically and technically feasible within required geometry andelectrical restrictions imposed in producing side-by-side characters ofuniform size and skew in very small spaces with tubes less than 1 inchin diameter.

Therefore, in accordance with this invention, individual cathode-raytubes placed side by side in line to fonn a line of characters are eachmade with cylindrical envelopes of less than 4 inches in length and .8inch in diameter to display individual characters of any desired shapeby scanning an electron beam electrostatically along two normal axes.

To provide acceptable alignment, each tube has an electron gun withelectrodes precisely positioned and oriented to produce ajbeam centeredon the phosphor screen raster area of approximately .625 inches maximumdeflection provided for character formation. This alignment isaccomplished in part by use of rectangular shaped electrode plates whichare held in two spaced glass beads oriented carefully in the center ofthe cylindrical envelope relative to a seven pin miniature stem todefine two normal deflection axes precisely within less than 3.

Those features of novelty afforded by this invention together withfurther objectives and advantages of the invention are illustrated bythe preferred embodiment shown in the accompanying drawings, wherein:

FIG. 1 is a schematic block diagram of a character display systemincorporating a plurality of side-by-side cylindrical cathode-ray tubecharacter-generating devices in accordance with the provisions of thisinvention.

FIG. 2 is a perspective view of a cathode-ray tube character generatorafforded by the invention.

FIG. 3 is a plan view of an electrode plate structure provided by theinvention.

FIG. 4 is an elevation schematic view of the electrode assembly andconnections to a miniature seven-pin stem, and

FIG. 5 is an elevation view of a cylindrical cathode-ray tube partlybroken away to show the electrode and connecting strap relationshipswithin the tube.

In FIG. 1 a set of separate cylindrical envelope CR display tubes 10,10' etc. is aligned along horizontal deflection axis 12 with theirphosphor faceplates substantially in the same plane. Each tube 10 has avertical deflection axis 11 which intersects at the center of thedisplay with the horizontal deflection axis 12.

When forming a line of separated characters, the alignment and skew iscritical if misalignments visually detectable are to be avoided. Forthis reason a character forming tube for presenting a singlecharacter-is critical in construction and must afford a combination offeatures which will provide precise centering and deflection alignmentin each individual tube without the necessity for external adjustment ormanipulation of electronic circuits. Conventional tube constructiontechniques in a tube of the very small size required with a screendiameter of less than 1 inch which would permit the beam to be offcenter as illustrated in tubes 10 and 10 by the dots, or which wouldallow deflection skew as illustrated in tubes 10" and 10" would beunacceptable in forming a line of characters. The eye is very sensitivein sensing character alignment, and even a small degree of skew ormisalignment is readily noticed as evidenced by viewing typewritten textwhen a type bar is slightly displaced, for example.

Character displays of any design can be generated for electrostaticallydeflecting the cathode-ray beam to form the numerical characters 2illustrated, or other desired pattern. Deflection techniques of thistype are well known and are represented by the block circuit diagram 15.The state of the art may be exemplified for example by reference to U.S.Pat. No. 3,432,845 issued Mar. 1 l, 1969, where numerical characters areproduced. It is to be noted that a CRT display of the type provided bythis invention is not restricted to any one set of characters or anylimitationson' variations or total number of characters possible. Also,by use of a P-l phosphor, the brightness significantly exceeds thatgenerally available with cathode glow, phosphorescent or other displayswhich generate their own light source.

Each tube is separately driven; at grid lead 17 and the horizontal andvertical deflection axes at leads 18, 19 by character generatorsubsections l6, 16' etc. to produce the desired line of text. In orderto display a line of characters on individual tubes it is significantthat the tube shape is cylindrical or equivalent nonflared shape withsubstantially symmetrical sidewalls permitting the tubes to be placedclosely together side by side along axis 12 and does not constitute aflared-out screen section found in conventional cathode-ray tubeoscillograph tubes.

Thus a tube 10 is preferably constructed as shown in FIG. 2, with acylindrical envelope having an axis 32 along which an electron beam isnominally directed in absence of electrostatic deflection voltages.Electrostatic deflection plates permit the tubes to be placed side byside without interference between tubes. In this tube, the electron gun30 is physically positioned in a precise manner to assure that theelectron beam is directed along centerline 32. This requires care inorienting each gun and deflection electrode exactly in place to be heldfirmly by a pair of glass beads 31. The beads are oriented in the regionof exhaust stem 39 and the miniature seven pin button to precisely alignthe deflection axes with respect to the pin socket positions. Thisisdone by straps or metallic posts welded carefully in place between theelectrodes and the pins inside the tube envelope to serve as leads andmounts to orient the deflection plates and stem in exact alignment. Toassure the centering of the beam within the cylindrical tube envelope, aset of special snubber springs is provided as hereinafter described tocenter the electron gun at a position remote from the stem.

in order to facilitate alignment and jigging for the precise electrodespacing and to seal the electrodes in the glass bead without distortion,electron lens electrodes 41, 53, 54, 55 are made rectangular in shape asshown in FIG. 3, to thus be embedded in the beads at opposed ends. Topermit electron gun flexibility with this preferred structure, thecentered beam aperture is selectively punched to the desired size foreach electrode but, otherwise, the various electrodes are similar, toprovide both low cost and better electron gun electrode alignment aswell as performance.

This critical snubber mount position is referenced in place in FIG. 4,where the snubber electrode or shield is held at ground potential byconnections to lead 65. The snubber plate 41 is physically mountedbetween beads 50, 51 in a position intermediate the two pairs ofdeflecting electrodes. The accelerating potential is applied betweenterminals 65 and 68.

The internal connections to the seven pins are illustrated, wheregrounded pin 65 leads to electrodes 41, 54, 55 and one electrode 63,etc., of each pair of deflection electrodes. Other connections are madeto the heater pin 66 and to the grid pin 67. Each deflection axis isavailable at a separate pin 69 and 71 connecting with respectivedeflection plates 64 and 62. A focus electrode such as cylinder 61 or anequivalent apertured plate structure is connected at pin 70 to makeavailable all the necessary electrode controls in a miniature seven-pinstem.

The gun structure has to be inexpensive to produce a competitive displaytube and yet very critical tolerances must be met. These tubes areconstructed with a centering requirement for an undeflected beam to liewithin one-half millimeter of the center of the tube in the scanningregion on the phosphor coated screen. Also the horizontal and verticaldeflection axes are oriented to within 3 of a reference axis defined bythe orientation of the pins in the seven-pin miniature stem. Theserequirements must be considered in view of the sensitivity of the beamto electrode positions and defects, and the normal tolerances of jigswith thermal changes of dimensions and stresses, etc. The very smalldimensions of the tube with a nominal cylinder diameter of .788 inches,tube length of 3.5 inches overall and useful screen deflection of .625inches, make the requirements even more critical.

These requirements are met, however, by the array shown in FIG. 4 wherethe electrodes are all aligned precisely between glass beads 50 and 51,held rigidly in place by the rectangular structure of the variouselectron gun electrodes 53, 54, 55 and 41 spaced along the gunstructure. This physically orients the electrodes precisely enough todirect the beam along a well-defined axis which is centered within thecylindrical tube envelope by the snubber springs to direct anundeflected spot precisely along the axis of the tube.

Also the deflection plates are oriented along normal axes by the beads50 and 51 to provide closely aligned deflection axes. Simple electrodestructures, such as the deflection plate 64 which is a single flat platebent along a straight line, provide for a minimum of distortion of thebeam by defects, corona or the like.

The rectangular lens structure with the oppositely extending tabsmounted in the pair of parallel glass beads permits also an improved andsimplified cathode mounting. Among their advantages is the simplicity ofjigs for holding the electrodes exactly in position while affixing aglass bead.

A cylindrical metallic cathode cup 57-59 is affixed by a tab to therectangular plate 52 without an intermediary ceramic disc or otherinsulator. The cathode cup 59 is preferably surrounded by a cylindricalshield 60 which is affixed to the plate by a suitable tab portion. Theshield 60 serves simultaneously to electrically shield the cathodeemission surface, provide proper heat conduction and dissipationcharacteristics and permit precise axial spacing of the cathode relativeto control grid 67 while maintaining exact alignment of the cathode withthe axis of the tube.

The overall tube perspective is shown from the view of FIG. 5, from theminiature seven-pin stem 29 to the phosphorcoated face 80, whereinconnection 65 corresponds to the connection schematically shown in FIG.4. An accelerating electrode inside the envelope comprising aquadagcoating 81 is contacted by a snubber spring assembly 42 attached torectangular electrode 41 formed as shown in FIG. 3.

In this tube the requirements for strict electrode alignment and verysmall space is accomplished by use of the rectangular electrodestructure. Very simple alignment jigs may be used and these electrodesfunctionally aid the electrostatic lens field formation, the shortnessof the overall tube, the ease of electrode connection and the ability tomake the electrodes and assemble the tube at reasonable cost. Note thenotched edges of the rectangular electrode structure. The notches whensymmetrically spaced prevent misalignment of the electron lens thatcould occur with irregular shapes and provides means for precisealignment of the parts. For this purpose, the

center aperture and the notches are cut with a single die to alwaysmaintain identical spaced relationships. Also the notches canfunctionally aid in connecting the electrode strap 65 for example ashereinafter described.

When the edges of electrodes 41, 63, 55 and 54 are disposed in the sameplane parallel to the beam axis, the connecting strap 65 may be simplywelded to the edges. lf several electrodes are encompassed by the strap,it may bypass certain electrodes such as the cylindrical focus electrode61 having a diameter small enough to prevent extending into the plane,or by notches in the edge of the rectangular plates.

In the embodiment shown, spaced deflecting plates of the pair 62 and 63have edges resting in the plane, but the path of strap 65 only passesover electrode 63. Rectangular plate 41 is located between two pairs ofdeflection plates so that the terminal end of strap 65 may be welded toa part of flared deflection electrode 64 that does not lie in the plane.

It is therefore clear that the novel arrangement of electrodes in thistube structure afford improved operation and simplified constructionparticularly in a miniature cathode-ray tube that must be preciselymatched with others for indicia generating applications.

lclaim:

1. A single gun cathode-ray tube assembly providing an axially centeredcathode ray beam path comprising in combination, an envelope having aphosphorous screen, an electron gun arrangement with a plurality ofspaced electrodes affixed in an ordered array extending along said axialpath of the cathode-ray beam by means of insertion of the electrodesinto two spaced molten beads into which the electrodes are extended and'means therewith to hold the beads firmly in a central position withinsaid envelope thereby to align the beam axis coaxially within theenvelope and to hold and direct the beam along a precisely directedaxial path to strike a predetermined position on said screen, saidspaced electrodes of said plurality being flat, rectangular plates ofthe same size, each having a single centered aperture therein andlongitudinal edges embedded in said spaced beads, and further havingunembedded edges substantially lying in a common plane parallel to thebeam axis defined by the single centered apertures of said plates, saidelectron gun arrangement further including interspersed with said flatelectrodes cylindrical electrodes of a sufficiently small diameter asnot to extend into the planes defined by the edges of said flatrectangular electrodes, a plurality of said rectangular electrodesfurther having sub stantially coplanar edges in a plane substantiallyparallel to said beam axis, and a connecting strap extending in saidplane and being attached to said coplanar edges.

2. A cathode ray tube assembly as defined in claim 1, including a set oftwo deflection plates having edges in said plane, and connections fromsaid strap to the edge of one of such deflection plates.

3. A cathode-ray tube assembly as defined in claim 1 wherein oppositeedges of said flat plates not embedded in said beads are provided withalignment notches extending inwardly from said common plane, whichnotches are precisely spaced relative to the single centered aperturestherein to provide alignment guides for precisely aligning the centeredapertures along said beam axis coaxially within said envelope.

1. A single gun cathode-ray tube assembly providing an axially centeredcathode ray beam path comprising in combination, an envelope having aphosphorous screen, an electron gun arrangement with a plurality ofspaced electrodes affixed in an ordered array extending along said axialpath of the cathode-ray beam by means of insertion of the electrodesinto two spaced molten beads into which the electrodes are extended andmeans therewith to hold the beads firmly in a central position withinsaid envelope thereby to align the beam axis coaxially within theenvelope and to hold and direct the beam along a precisely directedaxial path to strike a predetermined position on said screen, saidspaced electrodes of said plurality being flat, rectangular plates ofthe same size, each having a single centered aperture therein andlongitudinal edges embedded in said spaced beads, and further havingunembedded edges substantially lying in a common plane parallel to thebeam axis defined by the single centered apertures of said plates, saidelectron gun arrangement further including interspersed with said flatelectrodes cylindrical electrodes of a sufficiently small diameter asnot to extend into the planes defined by the edges of said flatrectangular electrodes, a plurality of said rectangular electrodesfurther having substantially coplanar edges in a plane substantiallyparallel to said beam axis, and a connecting strap extending in saidplane and being attached to said coplanar edges.
 2. A cathode ray tubeassembly as defined in claim 1, including a set of two deflection plateshaving edges in said plane, and connections from said strap to the edgeof one of such deflection plates.
 3. A cathode-ray tube assembly asdefined in claim 1 wherein opposite edges of said flat plates notembedded in said beads are provided with alignment notches extendinginwardly from said common plane, which notches are precisely spacedrelative to the single centered apertures therein to provide alignmentguides for precisely aligning the centered apertures along said beamaxis coaxially within said envelope.